Yuhong Fan

MHD simulations of CME with associated prominence eruption

whawkins — Tue, 16 Sep 2025 19:45:59 +0000

MHD simulations of CME with associated prominence eruption whawkins Tue, 09/16/2025 - 13:45

Author:

whawkins

Sep 16, 2025

Snapshots of the magnetic field lines (left column) and the synthetic SDO/AIA 304 Å images (right column) showing the development of a coronal mass ejection with associated prominence eruption in a MHD simulation of a prominence-forming coronal flux rope.

Solar Physics: We present an overview of magnetohydrodynamic (MHD) simulations of prominence-forming coronal flux ropes and the development of coronal mass ejection (CME) with associated prominence eruption. The simulations found the formation of a prominence-cavity system that qualitatively reproduces several observed features including the cavity, the prominence “horns”, and the central “cavity” enclosed in the “horns” above the prominence. We discuss the magnetic structure corresponding to these observed features and the effect of the prominence weight on the stability and eruption of the flux rope.

The Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) Code: A Global Corona Magnetohydrodynamic Code with the Yin-Yang grid

whawkins — Wed, 09 Apr 2025 20:43:41 +0000

The Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) Code: A Global Corona Magnetohydrodynamic Code with the Yin-Yang grid whawkins Wed, 04/09/2025 - 14:43

Author:

whawkins

Apr 9, 2025

The Astrophysical Journal Supplement: We describe the numerical algorithms of a global magnetohydrodynamic (MHD) code utilizing the Yin-Yang grid, called the Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) code, suitable for modeling the large-scale dynamical processes of the solar corona and the solar wind. It is a single-fluid MHD code taking into account the non-adiabatic effects of the solar corona, including the electron heat conduction, optically thin radiative cooling, and empirical coronal heating. We describe the numerical algorithms used to solve the set of MHD equations (with the semi-relativistic correction, or the Boris correction) in each of the partial spherical shell Yin Yang domains, and the method for updating the boundary conditions in the ghost-zones of the two overlapping domains with the code parallelized with the message passing interface (MPI). We validate the code performance with a set of standard test problems, and finally present a solar wind solution with a dipolar magnetic flux distribution at the solar surface, representative of solar minimum configuration.

The quasi-steady state solution from a global MHD simulation of the solar wind with a dipolar magnetic field, representative of the solar minimum condition. The magnetic field has reached a partially open configuration (top left panel) with open field lines (green and blue field lines) in the high latitude polar regions and closed field lines (red field lines) in the equatorial region under cusped field lines (orange field lines) which extend into an equatorial heliospheric current sheet (HCS). A transonic outflow reasonably close to the outflow in solar minimum coronal hole (Withbroe 1988) is obtained in the open field region. The synthetic white-light coronagraph image as would be observed from the equatorial earth view (top right panel) shows the bright equatorial helmet streamers made up by the closed and the cusped magnetic field lines and the dark coronal holes in the polar region made up by the open magnetic field, representative of the configuration typically seen in coronagraph (or eclipse) images during solar minimum. On the other hand, the synthetic coronagraph image as viewed from the pole (bottom right panel) shows striking dynamic features in the HCS due to the on-going 3D magnetic reconnection in the HCS. They show elongated dark (under-dense) wiggly features flowing sunward and truncate at the top of the helmet streamer. These features correspond to strong reconnection jets flowing sunward from the reconnection sites (see the red sunward flows of 𝑣𝑟 in the equatorial plane shown in the bottom left panel).

A data-driven MHD simulation of the 2011-02-15 coronal mass ejection from Active Region NOAA 11158

whawkins — Thu, 30 May 2024 19:34:54 +0000

A data-driven MHD simulation of the 2011-02-15 coronal mass ejection from Active Region NOAA 11158 whawkins Thu, 05/30/2024 - 13:34

Author:

whawkins

May 30, 2024

Result from the MHD simulation of the 2011-02-15 coronal mass ejection (CME) event of Active Region (AR) NOAA 11158: (a,b,c) Snapshots of the magnetic field evolution showing 3D field lines colored with the magnetic twist rate at three time instances during the onset of the eruption, (d,e,f) snapshots of the radial velocity in the middle meridional cross-section of the domain at the corresponding times of the 3D magnetic field images in the left column.

The Astrophysical Journal: We present a boundary data-driven magneto-hydrodynamic (MHD) simulation of the 2011-02-15 coronal mass ejection (CME) event of Active Region (AR) NOAA 11158. The simulation is driven at the lower boundary with an electric field derived from the normal magnetic field and the vertical electric current measured from the Solar Dynamics Observatory (SDO) Helioseismic Magnetic Imager (HMI) vector magnetograms. The simulation shows the build up of a pre-eruption coronal magnetic field that is close to the nonlinear force-free field (NLFFF) extrapolation, and it subsequently develops multiple eruptions. The sheared/twisted field lines of the pre-eruption magnetic field show qualitative agreement with the brightening loops in the SDO Atmospheric Imaging Assembly (AIA) hot passband images. We find that the eruption is initiated by the tether-cutting reconnection in a highly sheared field above the central polarity inversion line (PIL) and a magnetic flux rope with dipped field lines forms during the eruption. The modeled erupting magnetic field evolves to develop a complex structure containing two distinct flux ropes and produces an outgoing double-shell feature consistent with the Solar TErrestrial RElations Observatory B / Extreme UltraViolet Imager (STEREO-B/EUVI) observation of the CME. The foot points of the erupting field lines are found to correspond well with the dimming regions seen in the SDO/AIA observation of the event. These agreements suggest that the derived electric field is a promising way to drive MHD simulations to establish the realistic pre-eruption coronal field based on the observed vertical electric current and model its subsequent dynamic eruption.

Comprehensive analysis of a filament-embedding solar active region at different stages of evolution

whawkins — Fri, 09 Feb 2024 16:11:31 +0000

Comprehensive analysis of a filament-embedding solar active region at different stages of evolution whawkins Fri, 02/09/2024 - 09:11

Author:

whawkins

Feb 9, 2024

Astrophysical Journal Letters: Active regions are the brightest structures seen in the solar corona, so their physical properties hold important clues to the physical mechanisms underlying coronal heating. In this work, we present a comprehensive study for a filament-embedding active region as determined from observations from multiple facilities including the Chinese Hα Solar Explorer (CHASE). The spectral resolution of CHASE is as high as 0.024 ̊A pixel−1, which enables an accurate determination of the chromospheric Doppler velocity that is especially crucial for probing the relative stable structure investigated here. We find three types of dynamic features which correspond to different thermal and magnetic properties during the investigated time period, i.e., the overlying loops – 1MK cool loops, the moss region – 2∼3 MK hot loops, and the sigmoidal filament. The overlying cool loops,which have potential field, always show Doppler blue shifts at the east footprint and Doppler red shifts at the west, indicating a pattern of ‘siphon flow‘. The moss brightening region – the hot loops in the vicinity of the filament, which have moderate sheared field, always shows downward Doppler red shifts at the chromosphere, which could be a signature of plasma condensing into the inner region adjacent to the filament. The sigmoidal filament, which have severe sheared field lines along the polarity inversion line, however shows a different Doppler velocity pattern in its middle part, i.e., an upward Doppler blue shift at the double-J shaped stage and then a downward red shift after the sigmoidal filament forms. The present work shows overall properties of the filament-embedding active region, constraining the heating mechanisms of different parts of the active region and providing hints regarding the mass loading of the embedded filament.

Overview of the observations at Feb 14 (panels (a1)-(f1)) and 15 (panels (a2)-(f2)) is shown in the lower panels. Hα line center images from NVST and CHASE are displayed in panels (a1)-(a2) and (b1)-(b2), respectively. Panels (c1)-(c2) show the images from AIA/304 ̊A, and Doppler velocities obtained from CHASE are displayed in panels (d1)-(d2). The contours show the LOS magnetic field (Blos) with threshold values of ±100 G. Doppler velocity and AIA/171 ̊A with a larger FOV are shown in panels (e1)-(e2) and (f1)-(f2), respectively. Panels (g1)-(g2) show the vector magnetic field, with vertical magnetic field (Bver) in the background and the horizontal field (Bhor) overlaid on top as arrows. Red arrows show Bhor at positive polarity and blue arrows show Bhor at negative polarity. Pink and grey contours of ±5 G of the Bver are overlaid. Horizontal flows at the photosphere obtained from DAVE4VM are displayed in panels (h1)-(h2) with purple arrows showing the velocity at positive polarity and green arrows at the negative polarity. Grey and black contours of ±100 G of the Bver are also overlaid.

Recent Progress on Understanding Coronal Mass Ejection / Flare Onset by a NASA Living with a Star Focused Science Team

whawkins — Tue, 27 Jun 2023 20:19:25 +0000

Recent Progress on Understanding Coronal Mass Ejection / Flare Onset by a NASA Living with a Star Focused Science Team whawkins Tue, 06/27/2023 - 14:19

Author:

whawkins

Jun 27, 2023

Results from a data-driven MHD simulation of the 2011-02-15 X2.2 flare/CME event from Active Region NOAA 11158, using lower boundary driving condition derived from the vertical magnetic field and vertical electric current measured from the SDO/HMI vector magnetograms. Top panels show the 3D magnetic field just before the onset of the eruption, with the field lines colored in current density (panel (a)) and in twist rate (panel (b)). The middle row panels show the synthetic SDO/AIA 131 angstrom channel image (panel (c)) and synthetic SDO/AIA 94 angstrom channel image (panel (d)). The bottom panels show in comparison the observed SDO/AIA 131 angstrom channel image (panel (e)) and 94 angstrom channel image (panel (f)) at 2011-02-15 01:45 UT, about the time of the onset of the X2.2 flare.

Advances in Space Research: We present a report of recent progress on the topic of understanding solar coronal mass ejection (CME) onset from both modeling and observational viewpoints, as carried out from 2019 to the present by the NASA Living with a Star Focused Science Topic team on “Understanding the Onset of Major Solar Eruptions.” Following the typical Focused Science Topic paradigm, a number of research groups were selected and joined together to tackle this problem. The work being carried out by this team explores the role of topology and of helicity transport in creating an environment favorable to CME eruption and in then providing the energy required for CME onset. The team investigated CME energization and initiation via photospheric shearing, via flux rope formation, and via magnetic flux emergence. This article will highlight recent progress made by six American research groups working in these areas. We do not intend to present an exhaustive review of these topics, but rather summarize the ideas from these research groups regarding ongoing and upcoming challenges to the questions of how, when, and why coronal mass ejections erupt from the sun.

Comprehensive Radiative MHD Simulations of Eruptive Flares above Collisional Polarity Inversion Lines

whawkins — Thu, 22 Jun 2023 22:56:57 +0000

Comprehensive Radiative MHD Simulations of Eruptive Flares above Collisional Polarity Inversion Lines whawkins Thu, 06/22/2023 - 16:56

Author:

whawkins

Jun 22, 2023

ApJ: Matthias Rempel et al. present a new simulation setup using the MURaM radiative Magnetohydrodynamic (MHD) code that allows to study the formation of collisional polarity inversion lines (cPILs) in the photosphere and the coronal response including flares. In this scheme we start with a bipolar sunspot configuration and set the spots on collision course by imposing the appropriate velocity field at the footpoints in the subphotospheric boundary. We produce different setups with the same initial spot separation by varying physical parameters such as the collision speed and minimum collision distance. While all setups lead to the formation of an EUV and X-ray sigmoid structure, only the cases with a close passing of the spots cause flares and mass eruptions. The energy release is in the 1 − 2 × 10^31 ergs range, putting the simulated flares into the upper C-class to lower M-class range of GOES X- ray 1-8 ̊A flux. While the setup with the more distant passing of the spots does not lead to a flare, the corona is nonetheless substantially heated, suggesting non-eruptive energy release mechanisms. We focus our discussion on two particular setups that differ in spot coherence and resulting cPIL length persistence. We find different timings in the transition from a sheared magnetic arcade (SMA) to magnetic flux rope (MFR); the setup with a large length but shorter duration cPIL produces a MFR during the eruption, while the MFR is pre-existing in the setup with a large length and longer duration cPIL. While both result in flares of comparable strength and the eruption of a CME, the setup with pre-existing MFR (and embedded filament) leads to an MFR eruption with a larger mass content. Was published in October 2023.

Erupting magnetic flux rope. Field lines are color-coded by twist number. In addition we show a second set of field lines which are selected based on their connectivity to the reconnection region, these field lines are color-coded by temperature. We find tether-cutting reconnection underneath the ejected flux-rope. We show a cross-section through the erupting flux-ropes that display the mass density.

Hybrid data-driven magnetofrictional and magnetohydrodynamic simulations of an eruptive solar active region

whawkins — Thu, 22 Jun 2023 22:38:43 +0000

Hybrid data-driven magnetofrictional and magnetohydrodynamic simulations of an eruptive solar active region whawkins Thu, 06/22/2023 - 16:38

Author:

whawkins

Jun 22, 2023

The Astrophysical Journal: We present first results of the hybrid data–driven magnetofrictional (MF) and data–constrained magnetohydrodynamic (MHD) simulations of solar active region NOAA 11158, which produced an X-class flare and coronal mass ejection on 2011 February 15. First, we apply the MF approach to build the coronal magnetic configuration corresponding to the SDO/HMI photospheric magnetograms by using the JSOC PDFI SS electric field inversions at the bottom boundary of the simulation domain. We then use the pre-eruptive MF state at about 1.5 hour before the observed X-class flare as the initial state for the MHD simulation, assuming a stratified polytropic solar corona. The MHD run shows that the initial magnetic configuration containing twisted magnetic fluxes and a 3D magnetic null point is out of equilibrium. We find the eruption of a complex magnetic structure consisting of two magnetic flux ropes, as well as the development of flare ribbons, with their morphology being in good agreement with observations. We conclude that the combination of the data–driven MF and data–constrained MHD simulations is a useful practical tool for understanding the 3D magnetic structures of real solar ARs that are unobservable otherwise.

(left panel) Evolution of the plasma temperature enhancement near the bottom boundary of the simulation as a flare ribbon proxy, compared with (right panel) the EUV SDO/AIA 1600 A observation of flare ribbons. In the left panel, the light(dark)-grey contours represent positive (negative) radial magnetic field values of 300 G (dotted lines) and 30 G (solid lines), and the magnetic polarities are marked with the letters. The middle panel shows the reconnection flux derived from the simulated and the observed flare ribbon evolutions.

A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona

whawkins — Thu, 22 Jun 2023 22:10:31 +0000

A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona whawkins Thu, 06/22/2023 - 16:10

Author:

whawkins

Jun 22, 2023

ApJ: Feng Chen, Matthias Rempel, and Yuhong Fan present a comprehensive radiative magnetohydrodynamic simulation of the quiet Sun and large solar active regions. The 197 Mm wide simulation domain spans from 18(10) Mm beneath the photosphere to 113 Mm in the solar corona. Radiative transfer assuming local thermal equilibrium, optically thin radiative losses, and anisotropic conduction transport provide the necessary realism for synthesizing observables to compare with remote-sensing observations of the photosphere and corona. This model self-consistently reproduces observed features of the quiet Sun, emerging and developed active regions, and solar flares up to M class. Here, we report an overview of the first results. The surface magneto-convection yields an upward Poynting flux that is dissipated in the corona and heats the plasma to over 1 MK. The quiescent corona also presents ubiquitous propagating waves, jets, and bright points with sizes down to 2 Mm. Magnetic flux bundles emerge into the photosphere and give rise to strong and complex active regions with over 1023 Mx magnetic flux. The coronal free magnetic energy, which is approximately 18% of the total magnetic energy, accumulates to approximately 1033 erg. The coronal magnetic field is clearly non-force-free, as the Lorentz force needs to balance the pressure force and viscous stress as well as drive magnetic field evolution. The emission measure from log10T=4.5 to log10T>7 provides a comprehensive view of the active region corona, such as coronal loops of various lengths and temperatures, mass circulation by evaporation and condensation, and eruptions from jets to large-scale mass ejections.

Coronal dimming created in the quiet Sun by an emerging active region. Panel (a): Bz at the photosphere, before the active region emerges. Panel (b): Bz as in panel (a), but when a flux concentration (at (x,y) = (120,50)) starts to form. Panels (c) and (d): synthetic AIA 193 channel images from the top view. The time stamps are the same as in panels (a) and (b), respectively. The dimming region is visible in the lower half of the field of view. Panels (e) and (f): synthetic AIA 193 channel images from a side view along the y-axis. The time stamps are the same as in panels (a) and (b), respectively.

Eruption of a Magnetic Flux Rope in a Comprehensive Radiative Magnetohydrodynamic Simulation of flare-productive active regions

whawkins — Thu, 22 Jun 2023 21:59:41 +0000

Eruption of a Magnetic Flux Rope in a Comprehensive Radiative Magnetohydrodynamic Simulation of flare-productive active regions whawkins Thu, 06/22/2023 - 15:59

Author:

whawkins

Jun 22, 2023

ApJ: Feng Chen, Matthias Rempel, and Yuhong Fan present a radiative magnetohydrodynamic simulation that includes sufficiently realistic physics to allow for the synthesis of remote sensing observables that can be quantitatively compared with observations. We analyze the largest flare in a simulation of the emergence of large flare-productive active regions described by Chen et al. The flare releases 4.5×10^31 erg of magnetic energy and is accompanied by a spectacular coronal mass ejection. Synthetic soft X-ray flux of this flare reaches M2 class. The eruption reproduces many key features of observed solar eruptions. A pre-existing magnetic flux rope is formed along the highly sheared polarity inversion line between a sunspot pair and is covered by an overlying multi-pole magnetic field. During the eruption, the progenitor flux rope actively reconnects with the canopy field and evolves to the large-scale multi-thermal flux rope that is observed in the corona. Meanwhile, the magnetic energy released via reconnection is channeled down to the lower atmosphere and gives rise to bright soft X-ray post-flare loops and flare ribbons that reproduce the morphology and dynamic evolution of observed flares. The model helps to shed light on questions of where and when the a flux rope may form and how the magnetic structures in an eruption are related to observable emission properties.

Synthetic AIA 304 ˚A and 94 ˚A channel images from the viewpoint at the top of the domain. Large panels show the whole horizontal domain, while the inserts present a zoomed view of the source region of the eruption. Contour lines in the inserts mark Bz= ± 1500 G.

An improved MHD simulation of the 2006 December 13 coronal mass ejection of active region NOAA 10930

whawkins — Thu, 15 Dec 2022 17:07:48 +0000

An improved MHD simulation of the 2006 December 13 coronal mass ejection of active region NOAA 10930 whawkins Thu, 12/15/2022 - 10:07

Author:

whawkins

Dec 15, 2022

We present an magnetohydrodynamic (MHD) simulation of the coronal mass ejection (CME) on 13 December 2006 in the emerging $\delta$-sunspot active region 10930, improving upon a previous simulation by Fan (2016) as follows. (1) Incorporate an ambient solar wind instead of using a static potential magnetic field extrapolation as the initial state. (2) In addition to imposing the emergence of a twisted flux rope, also impose at the lower boundary a random electric field that represents the effect of turbulent convection, which drives field-line braiding and produces resistive and viscous heating in the corona. With the inclusion of this heating, which depends on the magnetic field topology, we are able to model the synthetic soft X-ray images that would be observed by the X-Ray Telescope (XRT) of the Hinode satellite, produced by the simulated coronal magnetic field. We find that the simulated pre-eruption magnetic field with the build up of a twisted magnetic flux rope, produces synthetic soft X-ray emission that shows qualitatively similar morphology as that observed by the Hinode/XRT for both the ambient coronal loops of the active region and the central inverse-S shaped ``sigmoid" that sharpens just before the onset of the eruption. The synthetic post-flare loop brightening also shows similar morphology as that seen in the Hinode/XRT image during the impulsive phase of the eruption. It is found that the kinematics of the erupting flux rope is significantly affected by the open magnetic fields and fast solar wind streams adjacent to the active region.

(a) Synthetic Hinode/XRT image at the time a few minutes before the onset of the eruption produced by the MHD simulation of the 2006 December 13 coronal mass ejection of active region NOAA 10930, compared with (b) the observed Hinode/XRT image about 3 minutes before the onset of the observed X-class flare. The simulated pre-eruption magnetic field with the buildup of a twisted magnetic flux rope, produces synthetic soft X-ray emission that shows qualitatively similar morphology as that observed by the Hinode/XRT for both the ambient coronal loops of the active region and the central inverse-S shaped "sigmoid" that sharpens just before the onset of the eruption.

Yuhong Fan

MHD simulations of CME with associated prominence eruption

Recent News

The Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) Code: A Global Corona Magnetohydrodynamic Code with the Yin-Yang grid

Recent News

A data-driven MHD simulation of the 2011-02-15 coronal mass ejection from Active Region NOAA 11158

Recent News

Comprehensive analysis of a filament-embedding solar active region at different stages of evolution

Recent News

Recent Progress on Understanding Coronal Mass Ejection / Flare Onset by a NASA Living with a Star Focused Science Team

Recent News

Comprehensive Radiative MHD Simulations of Eruptive Flares above Collisional Polarity Inversion Lines

Recent News

Hybrid data-driven magnetofrictional and magnetohydrodynamic simulations of an eruptive solar active region

Recent News

A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona

Recent News

Eruption of a Magnetic Flux Rope in a Comprehensive Radiative Magnetohydrodynamic Simulation of flare-productive active regions

Recent News

An improved MHD simulation of the 2006 December 13 coronal mass ejection of active region NOAA 10930

Recent News